JP2020194152A - Actuator, light scanning apparatus and object detecting apparatus - Google Patents

Abstract

To implement a scan in which a projection direction of a light beam periodically changes, with a configuration having low power consumption and high durability.SOLUTION: An actuator comprises: a column shaped permanent magnet 410 having an S-pole and an N-pole facing each other across a central axis, the movable magnet being supported by bearings 403, 405 rotatably around the central axis; a driving coil 420 disposed near the permanent magnet 410, the driving coil comprising a first portion 421 and a second portion 422 facing each other across the permanent magnet 410, the first portion including a wire bundle parallel to the central axis, the second portion including a wire bundle parallel to the central axis, where current flows in opposite directions in the first portion 421 and the second portion when powered on; a yoke 430 outside the driving coil 420, where the distance from the central axis to the yoke on a plane perpendicular to the central axis varies with a direction from the central axis; and a driving unit to apply a drive signal to the driving coil 420, the drive signal having a periodically varying voltage or current.SELECTED DRAWING: Figure 15

Description

The present invention includes an actuator that reciprocates a driven object, an optical scanning device that uses such an actuator, and an object detection device that detects an object on the optical path of the laser beam using such an actuator and a laser beam. Regarding.

Conventionally, an object detection device that detects an object on the optical path of the laser light and the distance to the object by irradiating the pulse of the laser light to the outside and detecting the laser light reflected by the object and returned. Are known. Such an object detection device is called a lidar (LiDAR: Light Detection and Ranging).
In recent years, riders have also come to be used in the field of autonomous driving of automobiles. In order to make up for the shortcomings of camera sensors that are easily affected by the external lighting environment and millimeter-wave radar with low resolution, and to accurately detect relatively small obstacles in the driving environment, we use camera sensors and millimeter-wave radar. It is used together.

Examples of riders that can be used in the field of autonomous driving are described in, for example, Patent Document 1. In the lidar described in Patent Document 1, a near-infrared laser as a light source and a photodetector as a receiver are arranged as a pair on a substrate according to a measurement angle, and in order to capture high-resolution distance information in the field of view. 32 or 64 sets of light source-receiver pairs are used. Therefore, the device is very large and expensive.

An example of another rider is described in Non-Patent Document 1. The rider described in Non-Patent Document 1 rotates a polygon mirror having three surfaces having different tilt angles, and deflects the laser beam with the polygon mirror within a viewing angle of 4.5 ° in the vertical direction. While projecting a laser beam, the reflected light from the object is reflected on the same surface as when projected by the polygon mirror and guided to the light detection element for detection.

In the lidar described in Non-Patent Document 1, one light receiving element can detect reflected light from a plurality of positions in the vertical direction. However, in the rider described in Non-Patent Document 1, since a polygon mirror having a different inclination angle for each reflecting surface is used, it is difficult to design the center of gravity thereof, and there is a problem that the cost is high in this respect.
A rider using a rotating mirror is also described in Non-Patent Document 2, but this document does not provide a detailed description of the rider configuration.

U.S. Pat. No. 8,767,190

Cristiano Niclass, et al., “A100-m Range 10-Frame / s 340 × 96-Pixel Time-of-Flight DepthSensor in 0.18-μm CMOS”, IEEE JOURNAL OF SOLID-STATE CIRCUITS, Institute of Electrical and Electronics Engineers, FEBRUARY 2013, VOL. 48, NO. 2, p. 559-572 Naoshige Shimizu, "Redundant systems and LiDAR Audi become pioneers of autonomous driving to realize Level 3", Nikkei Automotive, Nikkei BP Co., Ltd., September 2017, p. 22-23

By the way, in order to improve the detection accuracy and detection sensitivity of an object in a rider, it is desirable to scan a predetermined field of view with a laser beam at high speed and high density. On the other hand, it is important to reduce power consumption when considering the popularization of riders. In particular, when it is mounted on a small moving body in which it is difficult to provide a heavy battery, or when it is mounted on a wearable device such as glasses or a helmet, the power consumption restriction is remarkable. Further, in any case, it is of course preferable that the durability is high.
The techniques described in Patent Document 1, Non-Patent Document 1 and Non-Patent Document 2 have not been able to sufficiently meet such a demand regarding scanning.

The present invention has been made in view of such circumstances, and an object of the present invention is to realize scanning in which the projection direction of an optical beam is periodically changed with a configuration having low power consumption and high durability. The present invention is preferably applied to an object detection device such as a rider, but its application is not limited to object detection. The present invention can be applied to optical scanning for other purposes, and the use of the actuator of the present invention for applications other than optical scanning is not hindered.

In order to achieve the above object, the actuator of the present invention has a torsion spring fixed to a support member and an N pole fixed to the torsion spring on one side straddling the rotation axis of the torsion spring and on the other side. A permanent magnet on which the S pole is located, a drive coil arranged on the side opposite to the torsion spring of the permanent magnet, a drive unit for applying a drive signal whose voltage or current changes periodically to the drive coil, and the above. A mirror unit fixed to a torsion spring and arranged on the opposite side of the magnet, the first reflection surface located near the center of the torsion spring and the first reflection surface located around the first reflection surface. A mirror unit having a second reflecting surface parallel to the surface is provided, and the plane including the second reflecting surface is located closer to the rotation axis of the torsion spring than the plane including the first reflecting surface. The mirror unit reciprocates in response to the application of the drive signal.

In such an actuator, it is preferable that the center of gravity of the mirror unit is substantially on the rotation axis of the torsion spring.
Further, the mirror unit may include a first mirror having the first reflecting surface and a second mirror having the second reflecting surface.
Further, it is preferable that the center of gravity of the second mirror is closer to the rotation axis of the torsion spring than the center of gravity of the first mirror.

Further, it is preferable that the center of gravity of the mover including the torsion spring, the mirror unit, and the permanent magnet is substantially on the rotation axis of the torsion spring.
Further, the optical scanning apparatus of the present invention includes any of the above actuators, and projects a light beam after being reflected by the first reflecting surface of the mirror unit.

Further, in the object detection device of the present invention, after any of the above actuators, a laser light source for outputting a laser beam, a light receiving element, and the laser beam are reflected by the first reflecting surface of the mirror unit. An optical system that projects incident light to the outside and guides incident light incident from the outside on the same optical axis as the projected light to the light receiving element, the projection timing and projection direction of the laser beam, and the above. It is provided with an object detection unit that detects the distance of the laser beam to an object on the optical path and the direction of the object based on the timing of the light detection signal output by the light receiving element.
Such an object detection device may include a detection unit that detects the rotation speed of the mirror unit and a cycle control unit that controls the blinking cycle of the laser light source according to the rotation speed detected by the detection unit. ..

Further, another actuator of the present invention is a columnar magnet, which includes a magnet in which an S pole and an N pole face each other with a central axis in between, and a support portion that rotatably supports the magnet around the central axis. , A drive coil arranged in the vicinity of the magnet, including a first portion containing a bundle of conductors parallel to the central axis and a bundle of conductors parallel to the central axis, which is opposite to the first portion when energized. The second portion through which the current flows in the direction is a drive coil arranged at a position facing each other across the magnet and a yoke arranged outside the coil along the central axis, and is located on the central axis. A yoke in which the distance from the central axis to the yoke on a vertical plane differs depending on the direction from the central axis, and a drive unit for applying a drive signal whose voltage or current changes periodically to the drive coil are provided. It is a thing.

In such an actuator, the magnet may be prismatic or columnar.
Further, when no voltage is applied to the drive coil, the magnet moves toward a neutral position in a specific direction, and the first portion and the second portion of the drive coil are in the neutral position, respectively. It is preferable that the magnet is located at a position facing each magnetic pole of the magnet.
Further, the distance from the central axis to the yoke is equal between the north pole side and the south pole side of the magnet at the neutral position, and the north pole and the south pole of the magnet are at the center at the neutral position. It is preferable that the distance from the shaft to the yoke is the closest.

Further, the drive coil is connected to the one end portion of the second portion so that the lead wire wraps around the central axis of the magnet from one end portion of the first portion along the surface of the magnet. It is preferable that the magnet is formed so as to be connected to the other end of the first portion from the other end of the two portions so as to wrap around the central axis of the magnet along the surface of the magnet.
Further, it is preferable that the magnet reciprocates and rotates in a range centered on the position in the state where the drive signal is not applied in response to the application of the drive signal.
Further, a mirror fixed to the longitudinal end of the magnet is provided, and the mirror reciprocates in a range centered on the position in a state where the drive signal is not applied in response to the application of the drive signal. Exercise is good.

Further, another optical scanning device of the present invention includes the above-mentioned actuator, and projects a light beam after being reflected by the above-mentioned mirror.
In addition, another object detection device of the present invention reflects the above-mentioned actuator, the laser light source for outputting the laser beam, the light receiving element, and the above-mentioned laser beam by the above-mentioned mirror, and then projects the light to the outside, and also externally. The laser beam is based on an optical system that guides incident light incident from the light beam to the light receiving element, the projection timing and direction of the laser beam, and the timing of a light detection signal output by the light receiving element. It is provided with an object detection unit that detects the distance to an object on the optical path and a certain direction of the object.

In such an object detection device, it is preferable to provide a detection unit that detects the rotation speed of the mirror and a cycle control unit that controls the blinking cycle of the laser light source according to the rotation speed detected by the detection unit.
Further, the mirror of the actuator is provided with a second magnet at an end other than the magnet side, and the detection unit is provided with a magnetic sensor provided at a position facing the second magnet, and the magnetic sensor detects. It is advisable to detect the rotation speed of the mirror based on the fluctuation of the magnetism.
Further, the magnetic sensor may be a magnetic resistance sensor that detects the direction of the magnetic field by the magnetic resistance element.

Further, each of the above-described inventions can be carried out not only in the described modes but also in any mode such as an apparatus, a system, a method, a program, and a recording medium on which a program is recorded.

According to the present invention as described above, scanning in which the projection direction of the light beam is periodically changed can be realized with a configuration having low power consumption and high durability.

It is a block diagram which shows the main component of the object detection apparatus 10 which is one Embodiment of this invention by paying attention to the function. It is a figure for demonstrating the principle of the object detection in the object detection apparatus 10. It is an exploded perspective view which shows the structure of the main component of the object detection device 10. It is a perspective view which shows the appearance of the object detection apparatus 10. It is a figure which shows the schematic appearance and arrangement of the actuators 300, 380. It is an exploded perspective view which shows the structure of the component which comprises the actuator 300, and the outline of the assembly process. It is an exploded perspective view which shows the structure of the component which comprises the mover 320 of the actuator 300. It is a perspective view for demonstrating the whole structure of the mover 320 and explaining the function of the mirror unit 301. It is sectional drawing which looked at the cross section in the plane shown by the alternate long and short dash line of the actuator 300 shown in FIG. It is a figure for demonstrating the position of the center of gravity of the whole mover 320. It is a figure which shows the structure of the comparative example of a mover. It is a figure which shows the structure of the modification of the mirror unit. It is a figure which shows the schematic appearance and arrangement of the actuators 300, 380. It is a perspective view which shows the structure of the actuator 400. It is an exploded perspective view of the actuator 400. It is an exploded perspective view of the actuator 400 in a state of being disassembled more finely than FIG. It is a figure for demonstrating the principle of the reciprocating rotary motion performed by the actuator 400. It is another figure for demonstrating the principle of the reciprocating rotary motion performed by the actuator 400. It is a perspective view corresponding to FIG. 14 which shows the structure of the actuator 400'. It is an exploded perspective view corresponding to FIG. 15 which shows the structure of the actuator 400'. It is an exploded perspective view corresponding to FIG. 16 which shows the structure of the actuator 400'. It is a figure corresponding to FIG. 18 for demonstrating the principle of the reciprocating rotary motion performed by the actuator 400'. It is a figure which shows the structure of the modification of the yoke in the actuator 400. It is a figure which shows the structure of another modification of the yoke in the actuator 400. It is a figure which shows the structure of still another modification of the yoke in the actuator 400. It is a figure which shows the structure of the modification of the yoke in the actuator 400'. It is a figure which shows the structure of another modification of the yoke in the actuator 400'. It is a figure which shows the structure of still another modification of the yoke in the actuator 400'. It is a graph which shows the relationship between the scanning angle of the mirror unit 301, and the absolute value of the scanning angular velocity. It is a figure which shows the example of the drive signal of LD module 21. It is a figure which shows the example of the spot by the emitted light L2 formed on the scanning line when the drive signal of FIG. 26 is used. It is a figure which shows the structure of the control circuit for controlling the pulse interval of the drive signal of the LD module 21 together with the circuit around it. It is a figure which shows the example of the drive signal of the LD module 21 generated by the circuit of FIG. 28. It is a figure which shows the example of the spot by the emitted light L2 formed on the scanning line when the drive signal of FIG. 29 is used. It is a perspective view corresponding to FIG. 14 which shows the structure of the actuator 400 ″. It is a figure which shows the structure of the control circuit for controlling the pulse interval of the drive signal of the LD module 21 when the actuator 400 ″ is used, together with the circuit around it.

An embodiment of the present invention will be described with reference to the drawings.
[1. Overall configuration of the object detection device (FIGS. 1 to 4)]
First, the overall configuration of the object detection device according to the embodiment of the present invention will be described with reference to FIGS. 1 and 2 by classifying the main components by paying attention to their functions. FIG. 1 is a block diagram showing the main components of the object detection device by focusing on their functions. FIG. 2 is a diagram for explaining the principle of object detection in the object detection device.

The object detection device 10 according to an embodiment of the present invention projects a laser beam to the outside, detects a laser beam reflected by an external object and returns, and the projection timing and the detection timing of the reflected light. It is a device that detects the distance to an object on the optical path of the laser beam and the direction of the object based on the difference between the laser beam and the laser beam. As shown in FIG. 1, the object detection device 10 includes a light projecting unit 20, a scanning unit 30, a light receiving unit 40, a front-end circuit 51, a TDC (time-to-digital converter) 52, and a processor. 53, an input / output unit 54 is provided.

Of these, the light projecting unit 20 is a module for projecting a laser beam to the outside, and includes an LD (laser diode) module 21, a laser drive circuit 22, and a light projecting optical system 23.
The LD module 21 is a laser light source that outputs laser light according to a drive signal applied from the laser drive circuit 22. Here, the one provided with a plurality of light emitting points is used to increase the intensity of the output, but the number of light emitting points may be one. The wavelength of the laser light is not particularly limited, but for example, it is conceivable to use a laser light of near infrared light. Laser light is an example of a light beam.
The laser drive circuit 22 is a circuit for generating a drive signal for lighting the LD module 21 at a timing according to a parameter supplied from the processor 53 and applying the drive signal to the LD module 21. The LD module 21 is turned on intermittently by a pulse wave.

The projection optical system 23 is an optical system for converting the laser light output by the LD module 21 into a beam of parallel light. In this embodiment, the focal point is located at the center of a plurality of light emitting points included in the LD module 21. A collimated lens with a convex lens is used.
The laser beam L1 formed by the light projecting optical system 23 passes through the through hole 41a of the mirror 41 of the light receiving unit, is reflected by the mirror 31 of the scanning unit 30, and is used as the emitted light L2 outside the object detection device 10. Is output to.

Next, the scanning unit 30 is a module for deflecting the laser beam output by the light projecting unit 20 to scan in a predetermined field of view (FOV) 70, and is an actuator 32 having a mirror 31. To be equipped. The actuator 32 periodically changes the projection direction of the laser beam by periodically changing the direction of the mirror 31 provided on the optical path of the laser beam.

Further, although only one actuator 32 is shown in FIG. 1, the actuator 32 is actually composed of two actuators 300 and 400 that swing the mirror around different axes as shown in FIG. Then, the actuator 300 is in charge of scanning in the main scanning direction to form the main scanning direction (Horizontal) scanning line 71a, and the actuator 400 changes the direction of the mirror at the end of scanning in the main scanning direction to perform sub-scanning. Along with forming the vertical scanning line 71b, the scanning position in the sub-scanning direction is adjusted.
Since the LD module 21 lights up intermittently, the scanning lines 71 are actually a set of beam spots rather than continuous lines.
The above-mentioned light projecting unit 20 and scanning unit 30 constitute an optical scanning device.

Next, the light receiving unit 40 is a module for detecting light incident from the outside of the object detection device 10, and includes a mirror 41, a condenser lens 42, a light receiving element 43, and an aperture 44. The light to be detected by the light receiving unit 40 is a laser beam that is projected from the object detection device 10 and reflected by an external object and returned. The laser beam is diffusely reflected on the object surface, but only the component reflected in the direction opposite to the optical path at the time of projection returns to the object detection device 10 as return light L3. The return light L3 travels in the opposite direction along a path substantially the same as the emitted light L2, and reaches the mirror 41 as the return light L4.

The mirror 41 is a fixed mirror provided with a through hole 41a for passing the laser beam output from the light projecting unit 20 and for guiding the return light L4 to the light receiving element 43. At the position of the mirror 41, the return light L4 has a larger spread than the laser beam L1, so that it hits the mirror 41 in a wider range than the through hole 41a, and the component corresponding to the position other than the through hole 41a is reflected toward the light receiving element 43. Will be done.

The condenser lens 42 is a lens that collects the return light L4 reflected by the mirror 41 and forms an image on a predetermined focal plane.
The light receiving element 43 is a photodetecting element that outputs a detection signal according to the intensity of light that hits a predetermined light receiving surface. In this embodiment, a silicon photomultiplier (SiPM) is used as the light receiving element. This point will be described in detail later.
The aperture 44 is arranged on the focal plane of the condenser lens 42 and blocks light other than the aperture to prevent ambient light from entering the light receiving element 43.
Of the above, the mirror 41, the condenser lens 42, and the aperture 44 constitute a light receiving optical system.

Next, the front-end circuit 51 is a circuit that shapes the detection signal output by the light receiving element 43 into a waveform suitable for timing detection by the TDC 52.
The TDC 52 corresponds to the timing t0 of the lighting pulse of the laser beam L1 which is the emitted light based on the drive signal supplied from the laser drive circuit 22 and the detected detection signal after shaping supplied from the front end circuit 51. This is a circuit for forming a digital output indicating a time difference between the pulse timing t1 of the return light L4 and the return light L4.

Since there is a time difference between the pulse of the emitted light and the pulse of the return light, which is the time required for the light to reach and return to the object on the optical path, the object is detected as shown in FIG. 2 based on the time difference Δt. The distance s from the device 10 to the object can be obtained as s = c (Δt) / 2. c is the speed of light. To be exact, the above s is the optical path length from the object to the light receiving element 43.

The processor 53 is a control unit that controls the operation of each unit shown in FIG. It may be configured by a general-purpose computer having a CPU, ROM, RAM, etc. and executing software, may be configured by dedicated hardware, or may be a combination thereof. For example, the processor 53 calculates the distance to the object based on the output signal from the TDC 52, and calculates the direction of the object based on the scanning timing (the projection direction of the emitted light L2) by the scanning unit 30 at the time of detecting the return light. I do. Further, as will be described in detail later, the lighting interval of the LD module 21 is also controlled according to the orientation of the mirror 31 in the scanning unit 30.

The input / output unit 54 is a module that inputs / outputs information to / from the outside. Information input / output here includes wired or wireless communication with external devices, acceptance of operations from users using buttons, touch panels, etc., and users using displays, lamps, speakers, vibrators, etc. Includes presentation of information to. As the information to be output to the outside by the input / output unit 54, for example, it indicates that the information about the detected object (even the raw data of the distance and the direction has detected the object of a predetermined size, position, moving speed, etc. based on them). Information may be used), and information on the operating state and setting state of the object detection device 10 can be considered. As the information that the input / output unit 54 should receive the input from the outside, for example, the information related to the operation setting of the object detection device 10 can be considered.

As a communication partner by the input / output unit 54, for example, a mobile body such as a car or a drone equipped with an automatic driving system can be considered. If the information on the object detected by the object detection device 10 is supplied to the automatic driving system, the automatic driving system can refer to the information and plan a traveling route for avoiding the detected object.
It is also conceivable to implement the present invention as a system including the object detection device 10 and devices such as an automobile, a drone, and an aircraft with which the communication partner is communicated.

Next, the schematic structure of the object detection device 10 will be described with reference to FIGS. 3 and 4. FIG. 3 is an exploded perspective view showing the structure of the main components of the object detection device, and FIG. 4 is a perspective view showing the appearance of the object detection device.
As shown in FIGS. 3 and 4, the object detection device 10 includes an exterior in which the top cover 61 and the rear cover 62 are connected by two cover clips 63 and 63. Further, the top cover 61 is provided with a window for passing the emitted light L2, and the window is fitted with a protective material 64 transparent at the wavelength of the emitted light L2 to prevent dust from entering.

Each component shown in FIG. 1 is stored inside these housings. The actuator 32 shown in FIG. 1 is shown as two actuators, an actuator 300 that is in charge of scanning in the main scanning direction and an actuator 380 that is in charge of scanning in the sub-scanning direction. The mirror unit 301 is a mirror included in the actuator 300.
Further, although not shown in FIG. 1, the mirror 48 is an optical element located between the mirror 41 and the condenser lens 42 for changing the direction of the return light L4. The broken line 65 indicates the field of view of the object detection device 10 (scanning range by the emitted light L2) and corresponds to the field of view 70 in FIG. Wiring between circuits such as the laser drive circuit 22 and the processor 53 and modules is not shown in FIG. 3 for the sake of easy viewing.
This completes the description of the overall configuration, and hereinafter, some components of the object detection device 10 will be described individually.

[2. Configuration of scanning unit 30 and actuator 300 (FIGS. 5 to 11)]
Although it has already been described that the scanning unit 30 includes the actuators 300 and 380, since the actuator 300 has a characteristic configuration among these, this point will be described next.
FIG. 5 shows the schematic appearance and arrangement of the actuators 300 and 380 in an enlarged manner as compared with FIG.

As shown in FIG. 5, the actuator 300 and the actuator 380 have very different configurations.
Since the actuator 380 is used for deflecting the emitted light L2 in the sub-scanning direction, a very high-speed motion is not required. Therefore, an actuator of a type that rotates the mirror around a physical axis is used. The actuator 380 is configured by fixing the mirror 381 to the shaft 382, inserting the shaft 382 into the holder 383, and rotatably attaching the shaft 382. Then, due to the action of the permanent magnet and the coil arranged on the back side of the mirror 381, the mirror 381 rotates with the center of the shaft 382 as the rotation shaft 384 according to the voltage applied to the coil, and reciprocates within a predetermined angle range. To do. It is also possible to stop the mirror at a desired angle within the range of motion by adjusting the intensity of the voltage.

Such an actuator is called a galvanometer mirror. Generally, a configuration in which a mirror attached to the other end of the shaft is rotated by applying a force to one end of the shaft is widely used, but a position where a force is applied to the shaft and a mounting position of the mirror like the actuator 380 are widely used. However, even if they are at the same position in the longitudinal direction of the shaft, they can be driven by the same principle.

On the other hand, since the actuator 300 is used for deflecting the emitted light L2 in the main scanning direction, high-speed motion is required, and durability capable of continuing the high-speed motion for a long time is also required. Therefore, as the actuator 300, a new actuator suitable for such a purpose is used.

The specific configuration will be described in detail with reference to FIGS. 6 to 10, but in general, the actuator 300 has a mirror unit 301 having a protrusion on one surface of a torsion spring 302 having a linear protrusion. Is fixed so as to straddle the above, and the end portion of the torsion spring 302 is fixed to the top yoke 314 as a support member. Then, due to the action of the permanent magnet and the coil arranged on the other surface side of the torsion spring 302, the torsion spring 302 and the mirror unit 301 are substantially centered on the protrusion of the torsion spring 302 according to the voltage applied to the coil. It rotates around the rotation axis 304 located at, and reciprocates in a predetermined angle range.

The scanning unit 30 reflects the laser beam L1 by the mirror unit 301 and the mirror 381 driven by the actuators 300 and 380, respectively, and deflects the laser beam L1 to scan the emitted light L2 on the scanning line 71 shown in FIG. Can be projected to the outside.
Of course, it is not hindered to use an actuator having the same structure as the actuator 300 as the actuator that performs the deflection scanning in the sub-scanning direction.

Next, the structure and operating principle of the actuator 300 will be described in more detail with reference to FIGS. 6 to 12.
FIG. 6 is an exploded perspective view showing the structure of the parts constituting the actuator 300 and the outline of the assembly process thereof, and also includes a perspective view of the actuator 300 completed in the final process. FIG. 7 is an exploded perspective view showing the structure of the parts constituting the mover 320 of the actuator 300. FIG. 8 is a perspective view for showing the overall configuration of the mover 320 and explaining the function of the mirror unit 301. FIG. 9 shows a cross section (a cross section in a plane passing near the center of the plane portion 302b and perpendicular to the longitudinal direction of the protrusion 302c) in the plane indicated by the alternate long and short dash line of the actuator 300 shown in FIG. 6 (d). It is sectional drawing seen from the M direction. However, in order to make the figure easier to see, the coil assembly 313 is not shown in FIG. 9, and the coil winding method is schematically shown. FIG. 10 is a diagram for explaining the position of the center of gravity of the entire mover 320. FIG. 11 shows a comparative example, FIG. 12 shows a configuration of a modified example, and details will be described later.

As shown in FIG. 6A, the actuator 300 includes a core yoke 311, a frame yoke 312, a coil assembly 313, a top yoke 314, and a mover 320.
Of these, the frame yoke 312 and the top yoke 314 form an exterior made of a magnetic material surrounding the coil. The frame yoke 312 and the top yoke 314 are fixed so as to hold the coil assembly 313 inside by four screws 315 penetrating the four sets of screw holes 312b and 314b.

In the coil assembly 313, two coils of the drive coil 316 and the sensing coil 317 shown in FIG. 9 are wound around a bobbin 313a made of a non-magnetic material, and the outside thereof is covered with a protective cover 313c. Inside the bobbin 313a, an insertion hole 313b for passing the core portion 311a is provided. Further, the protective cover 313c includes a terminal for applying a drive signal to the drive coil 316 and a terminal for outputting a signal generated in the sensing coil 317 at a position not covered by the exterior.
The core yoke 311 includes a core portion 311a made of a ferromagnet, which is a core of the drive coil 316 and the sensing coil 317.

For each of these parts, the core portion 311a of the core yoke 311 is inserted into the insertion hole 312a of the frame yoke 312 as shown in (b) of FIG. 6, and then into the insertion hole 313b of the coil assembly 313 as shown in (c). The core portion 311a is inserted to position the coil assembly 313, and then the top yoke 314 and the frame yoke 312 are fixed by screws 315 and integrated as shown in (d).

At this time, the core portion 311a is fixed to the frame yoke 312 in the steps (a) to (b), and the coil assembly 313 is attached to the core portion 311a (and the frame yoke 312) in the steps (b) to (c). Fix it. This fixing can be done by using screws, welding, or gluing (not shown), by making the insertion side member slightly larger than the space on the receiving side and press-fitting it into the receiving position, or by combining these. It is conceivable to do.
In addition, in (b) and (c) of FIG. 6, the movable element 320 is not shown due to space limitations.

Further, as shown in FIG. 7, the mover 320 includes a mirror unit 301, a torsion spring 302, and a permanent magnet 321.
Of these, the torsion spring 302 is a spring formed by bending a metal plate by press working, folding, or the like, and is provided with a linear protrusion 302c having a V-shaped cross section by the fold. Further, near the center of the protrusion 302c, a flat surface portion 302b is provided on both sides so as to straddle the protrusion 302c, and a flat surface portion projecting on both sides so as to straddle the protrusion 302c is provided at both ends of the protrusion 302c. It includes 302a. These protrusions 302c and the flat surfaces 302a and 302b are all integrated, and by bending one plate-shaped member to form each of these parts, a torsion spring 302 having sufficient strength can be obtained at low cost. Can be formed.

Further, the flat surface portions 302a and the flat surface portions 302b at both ends are all located on the same plane in the natural state. However, when a force that rotates around the protrusion 302c is applied to the flat portion 302b while the flat portions 302a at both ends are fixed on the same plane, the protrusion 302c is twisted and the flat portion 302b is centered on the protrusion 302c. Rotate and move to. When the force is stopped, the restoring force of the spring eliminates the twist of the protrusion 302c, and the flat surface 302b returns to the same plane as the flat surface 302a.
Further, the permanent magnet 321 is fixed to the surface of the flat surface portion 302b opposite to the protrusion 302c so that the N pole 321n is located on one side straddling the protrusion and the S pole 321s is located on the other side. The positions of the N pole 321n and the S pole 321s may be opposite to those shown in the figure. The fixing between the permanent magnet 321 and the flat surface portion 302b can be performed by any method such as adhesion or welding.

The mirror unit 301 is configured by partially overlapping and adhering one first mirror 301a and two second mirrors 301b as shown in FIG. 7, and two second mirrors 301b. Is fixed to the torsion spring 302 by adhering to the surfaces of the flat surfaces 302b on both sides of the protrusion 302c on the side of the protrusion 302c. The adhesive used for these adhesions may be any one, but one having less curing shrinkage is desirable.

As shown in FIG. 9, the first mirror 301a and the tip of the protrusion 302c are not in contact with each other, and there is a slight gap. That is, the first mirror 301a is fixed only to the second mirror 301b, and the second mirror 301b serves as a spacer. This is because the protrusion 302c is slightly deformed when the torsion spring 302 is twisted, so that a certain amount of space is secured around the protrusion 302c so that the protrusion 302c does not interfere with the surrounding members even if the deformation occurs. This is because it is preferable to do so.

The above mover 320 is fixed to the mover holding portion 314a of the top yoke 314 in the step between (c) and (d) of FIG. 6 after assembling each member shown in FIG. 7 in advance. To do. This fixing is performed by screwing the flat surface portion 302a to the movable element holding portion 314a with a screw (not shown), or by adhering or welding the flat surface portion 302a and the movable element holding portion 314a, or the flat surface portion. It can be performed by any method such as inserting the 302a into the slit provided in the mover holding portion 314a.

In a state where the mover 320 is fixed to the top yoke 314, the flat surface portion 302b of the torsion spring 302 and the permanent magnet 321 face the coil assembly 313 through the opening 314c of the top yoke 314. More specifically, as shown in FIG. 9, one end of the shaft of the drive coil 316 provided in the coil assembly 313 faces the intermediate point between the N pole 321n and the S pole 321s of the permanent magnet 321. Seen from the permanent magnet 321, the drive coil 316 is arranged on the side opposite to the torsion spring 302.

When the drive coil 316 is energized in this state and, for example, the end of the permanent magnet 321 facing the permanent magnet 321 becomes an N pole, the S pole 321s of the permanent magnet 321 is attracted to the drive coil 316, and the N pole 321n becomes the drive coil 316. The repulsive force acts on the permanent magnet 321 to rotate it clockwise as seen in FIG. The force is transmitted to the flat surface portion 302b of the torsion spring 302, and the torsion spring 302 rotates clockwise around a virtual rotation axis 304 near the center of the cross section of the protrusion 302c and twists. Along with this, the mirror unit 301 fixed to the flat surface portion 302b also rotates clockwise around the rotation axis 304.
Then, the rotation stops at a position where the magnetic force generated between the drive coil 316 and the permanent magnet 321 and the restoring force of the torsion spring 302 are balanced. By changing the strength of the current flowing through the drive coil 316, the speed of rotation and the stop position can be adjusted.

Next, when the permanent magnet 321 and the mirror unit 301 are rotated clockwise to appropriate positions and the direction of energization of the drive coil 316 is reversed, the end on the side facing the permanent magnet 321 becomes the S pole. This time, the N pole 321n of the permanent magnet 321 is attracted to the drive coil 316, the S pole 321s repels the drive coil 316, and the permanent magnet 321 has a force to rotate counterclockwise as seen in FIG. work. The force is transmitted to the flat surface portion 302b of the torsion spring 302 as in the case of clockwise rotation, and the torsion spring 302 rotates counterclockwise around the rotation shaft 304 and twists in the opposite direction to the previous one. Along with this, the mirror unit 301 fixed to the flat surface portion 302b also rotates counterclockwise around the rotation axis 304.

By periodically reversing the direction of the voltage or current of the drive signal applied to the drive coil 316, the mirror unit 301 is alternately rotated clockwise and counterclockwise as shown by the arrow V in FIG. It is possible to make a reciprocating motion that rotates around the rotation shaft 304 within a predetermined angle range. That is, the mirror unit 301 can be swung on a predetermined movement path. As a result, the periodic deflection of the laser beam L1 required for scanning in the main scanning direction described with reference to FIG. 1 can be realized.

Considering the life of the torsion spring 302, it is desirable that the range of swing is symmetrical with respect to the natural state. But this is not mandatory. For example, by periodically switching the voltage applied to the drive coil 316 on and off, it is possible to swing within a predetermined range with a position near the natural state as one end. By periodically changing the voltage or current applied to the drive coil 316 within an appropriate range, the mirror unit 301 can be swung within an arbitrary swing range within the movable range of the torsion spring 302.

By the way, as shown in FIG. 8, in the mover 320, the mirror unit 301 reflects the laser beam L1 formed by the projection optical system 23 on the reflection surface (first reflection surface) of the first mirror 301a. The emitted light L2 is formed by appropriately deflecting the light. On the other hand, both the reflecting surface of the first mirror 301a and the reflecting surface (second reflecting surface) of the second mirror 301b reflect the return light L3 from the outside to the light receiving unit 40 on the same optical axis as the laser beam L1. It forms a return light L4 to be guided.

Of these, with respect to the emitted light L2, since the spot of the laser beam L1 is relatively small, the size of the first mirror 301a may be small, and the laser beam L1 is first reflected over the entire conceivable rotation range of the mirror unit 301. The size should be large enough to fit in the plane.

On the other hand, since the return light L4 is a part of the emitted light L2 reflected and diffusely reflected by the detection object, guiding the return light L4 in as wide a range as possible to the light receiving unit 40 is from the viewpoint of improving the detection sensitivity. preferable. Therefore, the total size of the first mirror 301a and the second mirror 301b is preferably as large as possible.

In the mirror unit 301, the first mirror 301a and the second mirror 301b are separately provided to increase the energy efficiency of rotation of the mirror unit 301 while ensuring a large reflection area, and to enable high-speed rotation. Because. That is, this is to enable high-speed scanning with low power consumption. This point will be further described.

First, consider a case where one mirror 501 having a sufficient size is provided so as to straddle the vicinity of the tip of the protrusion 302c as in the comparative example shown in FIG. In this case, a spacer that supports the mirror 501 on the flat surface portion 302b of the torsion spring 302 is also required, but the illustration thereof is omitted.
With such a configuration, a large mass of the mirror 501 is located at a position away from the rotation shaft 304 on the protrusion 302c side of the torsion spring 302, and the mover 320 related to the rotational movement around the rotation shaft 304. The moment of inertia of is large.

In order to avoid this and reduce the moment of inertia, it is conceivable to avoid providing the mirror 501 on the protrusion 302c and provide it on the flat surface 302b so as to approach the rotation shaft 304 as a whole. That is, it is conceivable to provide it at the position of the second mirror 301b. However, in this case, since the mirror must be provided so as to avoid the protrusion 302c, if a mirror having a size obtained by simply dividing the mirror 501 into two is provided at the position of the second mirror 301b, the end of the mirror will be a mirror. It is conceivable that it will be arranged at a place farther from the rotation shaft 304 than in the case of 501, and the moment of inertia will rather increase.

In order to solve such a problem, the mirror unit 301 is separately provided as a first mirror 301a straddling the protrusion 302c and a second mirror 301b arranged on the flat surface portion 302b, and a sufficient area is provided by the total. While ensuring, the position of the mirror is brought closer to the rotation axis 304 as a whole.

With this arrangement, the large-sized second mirror 301b can be brought closer to the rotation axis 304, and the moment of inertia related to the rotational movement about the rotation axis 304 can be made smaller than the arrangement shown in FIG.
That is, the size of the second mirror 301b can be reduced by the amount of the first mirror 301a, and the distance from the rotation shaft 304 to the end of the second mirror 301b can be prevented from becoming too long. Further, the first mirror 301a must be provided at a position some distance from the rotation shaft 304 in order to avoid the protrusion 302, but a size sufficient to straddle the protrusion 302 and be fixed to the second mirror 301b is sufficient. Therefore, the distance from the rotation shaft 304 to the end of the first mirror 301a can be prevented from becoming so large. Therefore, it is possible to avoid placing a large mass at a place far from the rotation shaft 304 and reduce the moment of inertia.

As a result, the energy required to twist the torsion spring 302 to rotate the mirror can be suppressed to a low level. Further, in the torsional vibration system, the resonance frequency is proportional to the 1/2 power of the value obtained by dividing the torsional rigidity K of the spring by the moment of inertia I. Therefore, if the moment of inertia is reduced, the resonance frequency of the mover 320 can be increased. It also contributes to speeding up scanning.
The reason why the first mirror 301a and the second mirror 301b are rectangular in the longitudinal direction along the rotation axis 304 is to reduce the moment of inertia.

In order to increase the resonance frequency of the mover 320, it is conceivable to use a spring having a large spring constant as the torsion spring 302. However, in order to make a spring having a larger spring constant, it is necessary to use a thicker metal plate, and as the thickness increases, the manufacturing error increases. Therefore, it is effective to increase the resonance frequency by adopting the mirror unit 301 having the shape as described above.

In order to obtain the above effect, if the mirror unit 301 is divided into a flat first mirror 301a and a second mirror 301b, it is easy to manufacture. However, it is not essential to configure it in this way. A single mirror in which the first mirror 301a and the second mirror 301b are integrated and has a step between the first reflecting surface and the second reflecting surface may be used. Further, one mirror 301'having a cross section as shown in FIG. 12 and in which the first reflecting surface 301a1 and the second reflecting surface 301b1 are smoothly connected may be used.
In any case, the example shown in FIGS. 6 to 10 is obtained by making the plane including the second reflecting surface closer to the rotation axis 304 of the torsion spring 302 than the plane including the first reflecting surface. As in the case of, the moment of inertia can be reduced and the resonance frequency can be increased.

Further, in addition to the above, in the mover 320, the center of gravity of the second mirror 301b is generally located on the rotation axis 304, so that the center of gravity of the remaining first mirror 301a, the permanent magnet 321 and the torsion spring 302 is also the rotation axis 304. By adjusting the size and weight of each part so as to be located above, the center of gravity 305 of the entire mover 320 can be placed on the rotation shaft 304 as shown in FIG.

In this way, by placing the center of gravity of the mover 320 substantially on the rotation shaft 304, it is possible to further increase the resonance frequency by preventing unnecessary vibration from being generated when the mirror unit 301 rotates due to the twist of the torsion spring 302. Can be done.
Even if the center of gravity of the mover 320 is not exactly on the rotation shaft 304, if the vibration due to the deviation of the center of gravity can be ignored, it can be regarded as the case where it is on the rotation shaft 304. Further, in the mover 320, since it is the mirror unit 301 that occupies a large weight, the center of gravity of only the part of the mirror unit 301 is on the rotation axis 304, or the position is slightly deviated from the permanent magnet 321. The center of gravity of the mover 320 can be approximately placed on the rotation axis 304.

Further, when the center of gravity of the cross section of the mover 320 in a plane perpendicular to the rotation axis 304 including the point is on the rotation axis 304 at all points on the rotation axis 304, the effect of increasing the resonance frequency is particularly large. .. However, even if the center of gravity of the entire mover 320 is somewhere on the rotation axis 304, a sufficiently meaningful effect can be obtained.

Further, in the actuator 300, the end portion of the mover 320 is fixed to the top yoke 314, but the portion near the flat surface portion 302b that actually moves is floating in the air, so that friction between parts occurs during swinging. It does not occur, and even if it is used continuously for a long time, heat generation and wear are unlikely to occur. Therefore, high durability can be obtained.
Further, since the coil assembly 313 is surrounded by the magnetic top yoke 314 and the frame yoke 312, leakage of the magnetic force generated in the drive coil 316 can be prevented and high drive efficiency can be obtained. However, it is not essential to provide such a magnetic material enclosure.

Further, the material of the torsion spring 302 may be, for example, stainless steel or phosphor bronze, but any other material capable of forming an elastic spring can be adopted. In addition, the reason why the cross section of the protrusion 302c is V-shaped is that a large spring constant was obtained by the simulations of the inventors, and it was found that the resonance frequency of the torsion spring 302 could be increased by this. is there.
However, the shape of the cross section is not limited to the V shape, and if it can function as a torsion spring, the cross section is angular n-shaped or U-shaped, or M-shaped, W-shaped, or an opening. Other shapes may be used, such as no air core thin wall closed cross section.

It should be noted that the structure having such a linear protrusion 302c can have higher rigidity in the direction orthogonal to the rotation axis than the torsion spring having a planar structure. This rigidity is very useful for performing stable scanning in an environment that constantly vibrates, such as in an automobile, and for ensuring the durability of the rocking portion.
Further, the torsion spring having the protrusion 302c has a three-dimensional shape and has a large thickness as a whole. For this reason, it is easy to bend the plate material to form it, but it is not possible to form a torsion spring having a sufficiently high protrusion 302c by a waher process using MEMS (Micro Electro Mechanical Systems) technology. ,Have difficulty.

Further, in the example of FIG. 9, the drive coil 316 is arranged in a direction perpendicular to the flat surface portion 302b in the natural state, but one end of the shaft is an intermediate point between the N pole 321n and the S pole 321s of the permanent magnet 321. The orientation is not limited to that shown in FIG. 9 as long as it faces. For example, even if the shaft is arranged in parallel with the protrusion 302c, the mirror unit 301 can swing as in the case of the configuration of FIG.

Further, it is not essential that the drive coil 316 is housed in the coil assembly 313 or wound around the bobbin, and the direct winding around the core portion 311a is not hindered.
Further, the sensing coil 317 is provided for adjusting the lighting timing of the laser beam L1 described later using FIGS. 25 to 30, and is unnecessary if this adjustment is not performed.

In addition to the above, it is not hindered to use an electromagnet that is energized when the mirror is driven, instead of the permanent magnet 321. However, the permanent magnet 321 is preferable because it has a simple structure, is less likely to cause an assembly error, and does not generate extra noise.

[3. Another configuration example of the actuator (FIGS. 13 to 23C)]
As the actuator provided in the scanning unit 30, instead of the actuator 300 described above, an actuator having a completely different operating principle can be adopted. Next, the actuator 400 will be described as an example of such another actuator.
First, FIG. 13 shows the schematic appearance and arrangement of the actuators 400 and 380 when the actuator 400 is provided instead of the actuator 300, in the same manner as in FIG.

As a general rule, the actuator 400 is configured by fixing a mirror 401 to a permanent magnet 410 and holding the permanent magnet 410 by bearings 403 and 405. Then, the interaction between the magnetic force of the permanent magnet 410 and the yoke 430 arranged around the permanent magnet 410 and the current flowing through the drive coil 420 (see FIG. 14) arranged between the permanent magnet 410 and the yoke 430. As a result, the permanent magnet 410 and the mirror 401 integrally rotate around the rotation axis 404 passing through the center of the permanent magnet 410 according to the voltage applied to the coil, and reciprocate within a predetermined angle range.

The scanning unit 30 reflects and deflects the laser beam L1 by the mirror 401 driven by the above actuator 400 and the mirror 381 driven by the same actuator 380 as shown in FIG. 5, so that FIG. 1 shows. The emitted light L2 that scans on the indicated scanning line 71 can be projected to the outside.
Of course, it is not hindered to use an actuator having the same structure as the actuator 400 as the actuator that performs the deflection scanning in the sub-scanning direction.

Next, the structure of the actuator 400 will be described in more detail with reference to FIGS. 14 to 16.
FIG. 14 is a perspective view showing the configuration of the actuator 400. 15 and 16 are exploded perspective views of the actuator 400, respectively. FIG. 16 shows a state in which the parts around the permanent magnet 410 are also disassembled as compared with FIG.
As shown in FIGS. 14 to 16, the actuator 400 includes a mirror 401, a mirror holder 402, a bearing 403, a bearing 405, a magnet holder 406, a permanent magnet 410, a drive coil 420, and a yoke 430.

Of these, the mirror 401 is a planar mirror having a reflecting surface for reflecting the laser beam L1 and the return light L4.
The mirror holder 402 fixes the mirror 401 to the bearing 403 so that its center of gravity is on the central axis (center of rotation) of the permanent magnet 410 and rotates with the rotation of the permanent magnet 410.

In the example of FIG. 14, the mirror holder 402 is fixed to the permanent magnet 410 by pushing the upper end of the columnar permanent magnet 410 into the thin-walled portion 402b formed so that the permanent magnet 410 fits. After that, the mirror holding portion 402a is passed through the inner ring 403a of the bearing 403 from the lower side to the upper side in the drawing, and the mirror holder 402 is pushed into the inner ring 403a as it is, so that the mirror holder 402 is fitted into the inner ring 403a and fixed. The mirror 401 is adhered to the mirror holding portion 402a.

Bearings 403 and 405 each hold a permanent magnet 410 so that it can rotate about its central axis.
The permanent magnet 410 is fixed to the bearing 403 via the mirror holder 402 as described above. To fix the permanent magnet 410 to the bearing 405, the end of the magnet holder 406 formed so as to fit the permanent magnet 410 was pushed against the magnet holding portion 406a to integrate the permanent magnet 410 and the magnet holder 406. Above, the bearing connection portion 406b of the magnet holder 406 is fitted into the inner ring 405a of the bearing 405.
As described above, the permanent magnet 410 and the mirror 401 are held by the bearings 403 and 405 so as to be integrally rotatable together with the inner ring 403a and the inner ring 405a.

Further, the drive coil 420 is fixed to the inside of the yoke 430 by adhesion or welding, and the yoke 430 is adhered or welded to the bearings 403 and 405 so as not to interfere with the rotation of the inner rings 403a and 405a. It is fixed.
The fixing methods such as fitting, bonding, and welding described above are examples, and it is of course possible to use other methods.

In the actuator 400, the permanent magnet 410 is a cylinder, and one side of the region in which the cylinder is divided into two in the radial direction is the N pole 410n and the other side is the S pole 410s (see FIGS. 17 and 18). It is not a configuration in which both ends in the longitudinal direction are N poles and S poles, respectively.

Further, the drive coil 420 includes a first portion 421 containing a bundle of conductors parallel to (the center of) the permanent magnet 410, and a bundle of conductors parallel to the permanent magnet 410, which is opposite to the first portion 421 when energized. The second portion 422 through which the electric current flows is arranged so as to face each other with the permanent magnet 410 interposed therebetween. The first portion 421 and the second portion 422 are connected by a first connection portion 423 and a second connection portion 424 arranged so as to wrap around the surface of the permanent magnet 410 near the end of the permanent magnet 410, respectively. ..

One turn of the drive coil 420, for example, raises the first portion 421 along the permanent magnet 410 from the bottom to the top in FIG. 14, enters the first connection portion 423 near the upper end of the permanent magnet 410, and enters the permanent magnet 410. Along the surface of FIG. 14, it wraps clockwise when viewed from above in FIG. 14, then enters the second portion 422, descends from top to bottom in FIG. 14 along the permanent magnet 410, and near the lower end of the permanent magnet 410. It enters the two connection portions 424, wraps around the surface of the permanent magnet 410 counterclockwise when viewed from above in FIG. 14, and is connected to the first portion 421 of the next lap. No lead wire is arranged at a position facing the end face in the longitudinal direction of the permanent magnet 410.

By using the drive coil 420 having this configuration, as will be described later, currents in different directions can flow through the N pole 410n side and the S pole 410s side with only one coil, and the N pole 410n side and the S pole 410s side. In addition, torque can be generated at the same time. Further, even if an electric current is passed through the first connection portion 423 and the second connection portion 424, no torque is generated for the permanent magnet 410, but since the length is short, the energy loss due to the resistance of the lead wire is large. It's less. For these reasons, the drive coil 420 can generate torque on the permanent magnet 410 with high energy efficiency.
Further, since the drive coil 420 having the above configuration can be formed only by bending the flat single air core coil into a U shape, it is easy to manufacture.

Although not shown, the actuator 400 is provided with terminals and wiring for applying a drive signal to the drive coil 420, and the drive coil 420 is provided so as not to come into contact with the permanent magnet 410.
The yoke 430 is a magnetic material arranged on the outside of the drive coil 420, and is composed of a continuous first portion 431, second portion 432, and third portion 433, respectively, of a flat plate, and the cross section is generally a square lacking one side. It is the shape of the remaining three sides of.

In the actuator 400 having the above configuration, the distance from the center of the permanent magnet 410 to the yoke 430 on the plane perpendicular to the center of the permanent magnet 410 differs depending on the direction viewed from the center of the permanent magnet 410. A yoke 430 is provided. That is, depending on the direction viewed from the permanent magnet 410, the permanent magnet 410 to the yoke 430 may be near or far from each other. In the direction of the missing side of the square without the yoke 430, the distance from the permanent magnet 410 to the yoke 430 can be considered to be infinite.

When the yoke 430 is provided in this way, when no voltage is applied to the drive coil 420, the N pole 410n and the S pole 410s of the permanent magnet 410 face each other in the direction in which the distance to the yoke 430 is the shortest due to the magnetic force. Stop. If both poles do not face the "closest direction", they will stop at the appropriate equilibrium position.

In the example of FIG. 14, one of the north pole 410n and the south pole 410s faces the vicinity of the center of the first portion 431, and the other faces the vicinity of the center of the second portion 432 and stops. Such a position will be referred to as a "neutral position". Then, even if the permanent magnet 410 rotates slightly from this position due to the voltage application to the drive coil 420, the permanent magnet 410 returns to the neutral position when the voltage application is stopped. In this sense, it can be said that the actuator 400 has a restoring force that returns the permanent magnet 410 to the neutral position. That is, it can be said that the permanent magnet 410 behaves like a spring whose neutral position is in the natural state in combination with the yoke 430.

When the actuator 400 is driven at a specific drive frequency as compared with a normal galvano mirror having a configuration in which a restoring force is not generated by causing the permanent magnet 410 and the mirror 401 to reciprocate and rotate using this restoring force, For example, if the actuator is driven at or near the resonance frequency of the moving part of the actuator, low power consumption and high-speed scanning are possible.
The distance from the permanent magnet 410 to the third portion 433 is preferably longer than the distance to the first portion 431 or the second portion 432. Even if the distance from the permanent magnet 410 to the third portion 433 is short, if one pole faces the third portion 433 side, there is no yoke facing the other pole, so this orientation is not in the neutral position. This is because a large disturbance may occur locally in the relationship between the orientation of the permanent magnet 410 and the strength of the restoring force.

Next, the principle of the reciprocating rotary motion performed by the actuator 400 will be described with reference to the explanatory views of FIGS. 17 and 18.
17 and 18 schematically show a state in which the cross sections of the permanent magnet 410, the drive coil 420, and the yoke 430 are viewed from the mirror 401 side in a plane perpendicular to the permanent magnet 410. However, cross-sectional hatching is omitted, and the yoke 430 shows only the first portion 431 and the second portion 432 that are involved in the formation of the neutral position. The arrows B and B'indicate the directions of the magnetic field lines generated by the permanent magnet 410 in each state. The arrows of the symbols F and F'indicate the direction of the force applied to the permanent magnet 410 in each state. In each case, the length of the arrow does not necessarily correspond to the magnitude of the force.

When the actuator 400 is left in a state where no voltage is applied to the drive coil 420 for a while, the permanent magnet 410 rotates to the neutral position shown in FIGS. 17A and 18A and stops. The positions of the north pole 410n and the south pole 410s are opposite to those in FIGS. 17 (a) and 18 (a), and the position where the north pole 410n faces the first portion 431 is also a neutral position. However, the same reciprocating rotary motion is possible, but here, the description will proceed assuming that the position shown in FIG. 17A is the neutral position.

A voltage is applied to the drive coil 420 from the state of FIG. 17 (a), and as shown in FIG. 17 (b), the current i from the front to the back of the paper surface is applied to the first portion 421, and the current i is applied to the second portion 422. Consider the state in which the opposite current-i from the back to the front is passed.
In this state, a clockwise magnetic field is formed around the first portion 421 and a counterclockwise magnetic field is formed around the second portion 422, and magnetic field lines are directed from the bottom to the top in the vicinity of the permanent magnet 410. A magnetic field is formed. The permanent magnet 410 receives a force from this magnetic field in the direction in which the N pole 410n faces upward, and rotates clockwise. This force can be considered to be a reaction of the Lorentz force generated by passing a current through the drive coil 420 in the magnetic field generated by the permanent magnet 410.
Then, when the voltage application to the drive coil 420 is stopped in the state of FIG. 17 (c) rotated to some extent, the permanent magnet 410 is caused by the magnetic force generated between each pole and the yoke 430 to be natural in FIG. 17 (a). Return to the state.

Further, as shown in FIG. 18 (b), when a voltage in the opposite direction to that in the case of FIG. 17 (b) is applied to the drive coil 420 and a current is passed in the opposite direction, magnetic field lines are generated in the vicinity of the permanent magnet 410. In the figure, a magnetic field is formed from top to bottom. The permanent magnet 410 receives a force from this magnetic field in the direction in which the N pole 410n faces downward, and rotates counterclockwise.
When the voltage application to the drive coil 420 is stopped in the state of FIG. 18 (c) rotated to some extent, the permanent magnet 410 is in the natural state of FIG. 18 (a) due to the magnetic force generated between each pole and the yoke 430. Return to the same state as in FIG. 17 (a)).

By applying a drive signal whose voltage or current changes periodically to the drive coil 420 and repeating the above process, the actuator 400 causes the permanent magnet 410 and the mirror 401 to reciprocate (swing). be able to.
The range of rotational motion may or may not be symmetrical with respect to the natural state. For example, by periodically switching the voltage applied to the drive coil 420 on and off, it is possible to swing within a predetermined range with a position near the neutral position as one end. By periodically changing the voltage or current applied to the drive coil 420 within an appropriate range, the mirror 401 can be swung within an arbitrary swing range.

In this case, when stopping the permanent magnet 410 at the end of the swing range, it is not necessary to apply energy to apply the brake, and it is sufficient to simply stop the voltage application to the drive coil 420. Further, it is not necessary to apply a voltage when returning the permanent magnet 410 from the end of the swing range to the neutral position. Therefore, when rotating the permanent magnet 410 from the neutral position to the end of the swing range, it is necessary to apply a voltage to the drive coil 420 that resists the restoring force to the neutral position. Even when added, the actuator 400 can swing the permanent magnet 410 and the mirror 401 with less power consumption than the galvano mirror having no restoring force.

If the rotation angle of the permanent magnet 410 becomes too large during swinging, the permanent magnet 410 does not return to the original neutral position when the voltage application is stopped, and the N pole 410n and the S pole 410s are switched to the neutral position. There is a possibility of migration. Therefore, it is preferable that the swing range is not so large. In the examples of FIGS. 17 and 18, rotation should not be more than ± 90 ° from the initial neutral position.

There is also a problem that the energy efficiency decreases as the displacement from the natural state increases. This is because as the displacement increases, each pole is affected not only by the conducting wires that were naturally opposed to each other, but also by the conducting wires on the opposite side. This effect acts as a brake on rotation because a current flows through the opposite wire in the opposite direction to the naturally opposed wire.
From these viewpoints, it is preferable that the range of rotational motion is symmetrical with respect to the natural state because high energy efficiency can be obtained while widening the swing range.

In the actuator 400 described above, the permanent magnet 410 is cylindrical, but the shape of the permanent magnet is not limited to this. Since the columnar shape has high symmetry, the stability of rotation can be improved, but it is not necessary to have a columnar shape as long as the bearing, holder, or the like can be rotatably held in an appropriate shape. For example, it may be prismatic. Further, in the case of a cylinder or a prism, not only a rod shape having a height larger than the size of the bottom surface but also a disk shape having a diameter of the bottom surface larger than the height can be taken. Further, it is not hindered that the cross-sectional area differs depending on the position in the height direction, for example, a barrel-shaped shape having a large cross-sectional area near the central portion or a shape having a large cross-sectional area near the end portion.

Here, the configuration of the actuator 400'in which the permanent magnet is a prismatic shape is shown in FIGS. 19 to 21. 19 to 21 are perspective views or exploded perspective views corresponding to FIGS. 14 to 16 showing the configuration of the actuator 400, respectively. In FIGS. 19 to 21, the same parts as the actuator 400 are designated by the same reference numerals as those in FIGS. 14 to 16.
In the actuator 400', the permanent magnet 410' is a quadrangular prism and has a rectangular cross-sectional shape on a plane perpendicular to the rotation axis (see FIG. 22). Correspondingly, the shape of the thin portion 402b'of the mirror holder 402'in which the permanent magnet 410'is fitted and the magnet holding portion 406a' of the magnet holder 406' also have a rectangular cross section. Other parts are the same as the actuator 400. The mirror holding portion 402a of the mirror holder 402'and the bearing connecting portion 406b of the magnet holder 406' also have the same shape as that of the actuator 400.

As described above, even if the permanent magnet 410'has a rectangular cross section, the neutral position is set by the magnetic force generated between the N pole 410n'and the S pole 401s' and the yoke 430, as in the case of the permanent magnet 410 of the actuator 400. Can have. Further, the permanent magnet 410'receives a force in the rotating direction due to the magnetic field generated by the current flowing through the drive coil 420, and returns to the neutral position when the current flowing through the drive coil 420 disappears, as in the case of the actuator 400. .. FIG. 22 shows the force received by the permanent magnet 410'in the actuator 400', using the example corresponding to FIG.

Next, a modified example of the shape of the yoke 430 will be described.
The shape of the yoke 430 is also not limited to that shown in FIGS. 13 and 14. For example, in the actuator 400, the shapes shown in FIGS. 23A to 23C can also be adopted. 23A to 23C schematically show the cross-sectional shape of the yoke in a plane perpendicular to the permanent magnet 410 together with the cross-sectional shapes of the permanent magnet 410 and the first portion 421 and the second portion 422 of the drive coil 420. ing.
A similar shape can be adopted for the actuator 400', and configuration examples in this case are shown in FIGS. 24A to 24C. However, since the function of the yoke of each shape is the same as that of the actuator 400, it will be described as a representative with reference to FIGS. 23A to 23C.

The yoke 440 shown in FIG. 23A has a shape in which one side is open like the yoke 430, but unlike the yoke 430, the lower portion is a curved curved surface portion 443 in the figure corresponding to the second portion 432. The yoke may have a shape including a curved surface in this way.
The yoke 450 shown in FIG. 23B has a rectangular cross section and has a shape that covers the entire circumference of the permanent magnet 410 (however, it is not necessary to cover the end portion in the longitudinal direction). Even if the entire circumference is covered in this way, a portion near the center of the permanent magnet 410 (first portion 451 and second portion 452) and a portion far from the center (other portions) are formed on the yoke 450, and the portion close to the center. If the permanent magnets 410 are arranged so as to face each other, the positions where the magnetic poles of the permanent magnets 410 face the close portions are the neutral positions, and the reciprocating rotational motion of the permanent magnets 410 similar to that described with reference to FIGS. 13 to 18 is performed. It is possible.

The yoke 460 shown in FIG. 23C also has an elliptical cross section and has a shape that covers the entire circumference of the permanent magnet 410. In this way, even if the entire yoke 460 is composed of a continuous curved surface, a portion near the center of the permanent magnet 410 (a portion indicated by reference numerals 461 and 462) and a portion far from the center (other portions) are formed and the portions are close to each other. If the portions are arranged so as to face each other, the permanent magnet 410 can reciprocate and rotate as in the case of FIG. 23B. However, from the viewpoint of ease of the process of fixing the drive coil 420 to the yoke 430, an arrangement in which the drive coil 420 can be fixed to a flat surface portion like the yoke 450 is preferable.

It should be noted that at least the first portion 431 and the second portion 432 of FIG. 17 form the neutral position of the permanent magnet 410, and the permanent magnet 410 reciprocates in the same manner as described with reference to FIGS. 13 to 18. Rotational movement is possible. The width of the first portion 431 and the second portion 432 may be narrow. However, it is preferable to cover the circumference of the permanent magnet 410 as widely as possible from the viewpoint of forming a closed magnetic path and efficiently using the magnetic force of the permanent magnet 410 for rotational motion. From this point of view, the yoke 450 and the yoke 460 have a shape that covers the entire circumference of the permanent magnet 410.
However, if the entire circumference of the permanent magnet 410 is covered, the magnetic poles of the permanent magnet 410 are attracted in all directions, so that the restoring force toward the neutral position is weakened. From this point of view, it can be said that a configuration in which one direction is open, such as the yoke 430 and the yoke 440, is preferable because the restoring force to the neutral position can be strengthened.

For example, in FIG. 23B, even if the distance from the center of the permanent magnet 410 to the first portion 451 of the yoke 450 and the distance to the second portion 452 are different, if the neutral position of the permanent magnet 410 is determined. , The reciprocating rotational movement of the permanent magnet 410 similar to that described with reference to FIGS. 13 to 18 is possible.
Further, in FIG. 23A, even if the distance to the curved surface portion 443 is closer than the distance from the center of the permanent magnet 410 to the first portion 441 and the second portion 442 of the yoke 440, the opposite side of the curved surface portion 443. Since there is no yoke in the magnet, it is conceivable that both magnetic poles of the permanent magnet 410 are stable in the directions facing the first portion 441 and the second portion 442, respectively, and the positions are in the neutral position. As described above, even in the case where the magnetic pole of the permanent magnet 410 does not face the side closest to the yoke 440 in the neutral position, if there is a stable neutral position, the permanent magnet is the same as that described with reference to FIGS. 13 to 18. The reciprocating rotational movement of the magnet 410 is possible.

However, in the neutral position, the distance from the center of the permanent magnet 410 to the yoke is equal on the N pole 410n side and the S pole 410s side, and both magnetic poles have the shortest distance from the center of the permanent magnet 410 to the yoke. If the shape and arrangement of the yoke 440 are determined so as to face the direction, the relationship between the direction of the permanent magnet 410 and the strength of the restoring force will not be greatly disturbed during the rotational movement of the permanent magnet 410, and will be permanent. This is preferable from the viewpoint of the rotational stability of the magnet 410.

Further, regarding the neutral position, when there is one neutral position, the position where the N pole and the S pole are exchanged by rotating the permanent magnet 410 by 180 ° from that position is also the neutral position. However, it is not desirable to have a neutral position other than those two. If the permanent magnet 410 is rotated from one neutral position to a position close to the other neutral position, the permanent magnet 410 will not return to the original neutral position. Therefore, if there are two or more sets of neutral positions, the reciprocating rotary motion will occur. This is because the range cannot be taken large. For example, if the cross section of the yoke is square and its center coincides with the center of the permanent magnet 410, four neutral positions will occur every 90 °. Even with such a configuration, if the reciprocating rotary motion is less than ± 45 °, it is possible in the same manner as that described with reference to FIGS. 13 to 18, but the motion is as compared with the case where there are only two neutral positions. The possible range becomes narrower.

Further, regarding the drive coil 420, it is preferable that the first portion 421 and the second portion 422 are located as close as possible to the magnetic poles of the permanent magnet 410 in the neutral position. This is because the influence of the magnetic field due to the current flowing through these parts is strongly exerted on the permanent magnet 410. Then, the first portion 421 and the second portion 422 are arranged at a position where the yoke is behind the permanent magnet 410, and this arrangement also contributes to firmly fixing the drive coil 420 to the yoke. ..

[5. Control of beam lighting interval according to scanning position in main scanning direction (FIGS. 25 to 30)]
Next, control of the beam lighting interval according to the scanning position of the emitted light L2 in the main scanning direction will be described.
The control described here is a control applied when the actuator 300 is used for the scanning unit 30. In this case, since the scanning position in the main scanning direction corresponds to the orientation of the mirror unit 301 (particularly the first mirror 301a) in the actuator 300, the control described here is also a control according to the orientation of the mirror unit 301. ..

First, the characteristics of the swinging operation of the mirror unit 301 by the actuator 300 will be described with reference to FIGS. 25 to 27.
FIG. 25 is a graph showing the relationship between the scanning angle of the mirror unit 301 and the absolute value of the scanning angular velocity, FIG. 26 is a diagram showing an example of a drive signal of the LD module 21, and FIG. 27 is an output formed on a scanning line. It is a figure which shows the example of the spot by the light emission L2.

Experiments by the inventors have shown that the moving speed of the mirror unit 301 swung by the actuator 300 is not constant. Since the mirror unit 301 stops at the end of the swing path and moves at other parts, it is clear that the moving speed fluctuates, but the speed is generally that of the swing path, as shown in FIG. It is slower toward the edges and faster toward the center. When rotating counterclockwise or clockwise, only the direction of movement is different, and the speeds are almost the same if they are in the same position.

Therefore, in FIG. 25, the position on the swing path (expressed by the angle of rotation and referred to as “scanning angle”) is taken on the horizontal axis, and the absolute value of the angular velocity at that position is taken on the vertical axis. The change is illustrated.
Since the rotation speed of the mirror unit 301 fluctuates in this way, when the LD module 21 is driven by the drive signal drv1 having pulses at equal intervals as shown in FIG. 26, the scanning line 71 is shown in FIG. 27. A spot 72 of the emitted light L2 is formed. That is, spots that are coarse at the center in the main scanning direction and finely distributed at the edges are formed. Therefore, the detection resolution of the object is also coarser at the central portion than at the edge portion.

When considering the detection of obstacles as an application of the object detection device 10, this state is not preferable because it is considered that the vicinity of the center of the visual field is the most important.
Therefore, the object detection device 10 is provided with a control circuit for controlling the pulse interval of the drive signal of the LD module 21 according to the scanning angle of the mirror unit 301.

FIG. 28 shows the configuration of the control circuit.
The control circuit 351 shown in FIG. 28 corresponds to a periodic control unit, and is roughly divided into operations related to drive control of the drive coil 316, detection of the rotation speed of the mirror unit 301, and control of the lighting interval of the LD module 21.

First, regarding the drive control of the drive coil 316, the control circuit 351 sets the scan range and the period value to be executed by the actuator 300 with respect to the drive signal generation circuit 352 that generates the drive signal 353 applied to the drive coil 316. To do. The drive signal generation circuit 352 generates a drive signal 353 of an appropriate level having a voltage fluctuating at an appropriate cycle according to the set value and applies it to the drive coil 316 of the actuator 300. As a result, the mirror unit 301 can be swung by the actuator 300 as described with reference to FIG. 9 and the like.

Next, regarding the detection of the rotation speed of the mirror unit 301, the detection circuit 354 detects the induced voltage generated in the sensing coil 317 of the actuator 300, and the ADC (analog-digital converter) 355 converts the voltage into a digital value in real time. Then, the value is corrected by the difference calculation unit 357 and supplied to the control circuit 351. The control circuit 351 calculates the rotation speed of the mirror unit 301 based on the voltage value. The number of turns of the sensing coil 317 is the same as that of the drive coil 316, and may be reversed from that of the drive coil 316, but the number of turns is not limited to this.

Here, when the mirror unit 301 is swung, an induced electromotive force is generated in the sensing coil 317 due to two kinds of factors.
The first factor is the induced electromotive force due to fluctuations in the strength and direction of the magnetic field generated by the drive coil 316 due to voltage fluctuations in the drive signal applied to the drive coil 316.
The second factor is the induced electromotive force due to the fluctuation of the strength of the magnetic field caused by the swing of the permanent magnet 321. When the permanent magnet 321 swings as described with reference to FIG. 9 and the like, the fluctuation speed of the magnetic field strength generated in the sensing coil 317 can be considered to be substantially proportional to the rotation angular velocity of the permanent magnet 321. .. Since the rotational angular velocity of the permanent magnet 321 is also the rotational angular velocity of the mirror unit 301, it can be considered that the strength of the induced electromotive force generated by the second factor is proportional to the rotational angular velocity of the mirror unit 301.

The mutual induction voltage pattern storage unit 356 and the difference calculation unit 357 are provided to subtract the value of the induced electromotive force due to the first factor from the output of the ADC 355.
That is, the mutual induction voltage pattern storage unit 356 changes the voltage value of the induction voltage generated in the sensing coil 317 by mutual induction when the drive signal is applied to the drive coil 316 with the permanent magnet 321 removed in the actuator 300. , One cycle of the drive signal is stored in association with the phase of the drive signal. Then, when the drive signal generation circuit 352 applies the drive signal to the drive coil 316 in order to swing the mirror unit 301, the drive signal generation circuit 352 supplies a timing signal indicating the phase of the drive signal to the mutual induction voltage pattern storage unit 356. .. Based on this timing signal, the mutual induction voltage pattern storage unit 356 supplies the voltage value corresponding to the current timing to the difference calculation unit 357.

The difference calculation unit 357 subtracts the voltage value supplied from the mutual induction voltage pattern storage unit 356 from the value of the induced voltage actually generated in the sensing coil 317 supplied from the ADC 355 as the contribution of mutual induction. , The resulting difference is supplied to the control circuit 351.
As described above, the value of the induced voltage proportional to the rotational angular velocity of the mirror unit 301 can be supplied to the control circuit 351. When the change in the induced voltage supplied to the control circuit 351 is plotted with the time for half a cycle from one end to the other end of the swing range of the mirror unit 301 on the horizontal axis, it is shown in FIG. 25 as shown in Graph 361. It is considered that the shape is almost the same as the graph of the rotational angular velocity shown.

The control circuit 351 multiplies the voltage value VR (t) supplied from the difference calculation unit 357 at time t by the proportionality constant K obtained and set in advance to obtain the angular velocity ω (t) of the mirror unit 301. It is calculated by t) = K × VR (t).
The value of K is obtained, for example, by comparing the value obtained by measuring the rotation angle of the mirror unit 301 for half a cycle by another means with the integrated value of the voltage value VR (t) for half a cycle.

Further, the control circuit 351 can use ω (t) to determine the lighting interval T for lighting the LD module 21 so that a desired resolution can be obtained on the scanning line 71a in the main scanning direction. Assuming that the resolution is ψ degree, T = π · (ψ / 180) / ω (t).
In order to control the lighting interval of the LD module 21, the control circuit 351 obtains the lighting interval T in real time according to the supply of the voltage value VR (t) from the difference calculation unit 357, and a pulse indicating the value of T. The width modulation signal is supplied to the pulse generator 358.

The pulse generator 358 performs pulse width modulation according to the pulse width modulation signal, generates a timing signal having a pulse of interval T, and supplies the timing signal to the laser drive circuit 22. The laser drive circuit 22 generates a drive signal for lighting the LD module 21 at the timing of the pulse included in the timing signal supplied from the pulse generator 358, and supplies the drive signal to the LD module 21.

Graph 362 shows the pulse interval supplied by the control circuit 351 to the pulse generator 358 from one end to the other end of the swing range of the mirror unit 301 with the time on the horizontal axis as in graph 361. become. That is, the control circuit 351 is a mirror unit when the mirror unit 301 is near the center of the swing path and the induced voltage is at a high level (first level) according to the induced voltage generated in the sensing coil 317. The control is performed so as to shorten the blinking cycle of the LD module 21 as compared with the case where 301 is near the end of the swing path and its induced voltage is at a low level (second level).

As a result, the drive signal of the LD module 21 generated by the laser drive circuit 22 has a different pulse interval depending on the moving speed of the mirror unit 301, as shown in drv2 shown in FIG. Then, as shown in FIG. 30, the beam spot 72 obtained by deflecting the laser beam L1 whose lighting is controlled by the mirror unit 301 is approximately over the entire length of the scanning line 71a in the main scanning direction. It will be arranged at equal intervals. As a result, the object detection device 10 can detect the object within the field of view 70 with substantially uniform resolution.
As for the sub-scanning direction, since the mirror 381 is stationary while scanning one line in the main scanning direction, the above-mentioned problems do not occur and the lighting interval does not need to be adjusted.

The control circuit 351 described above may be provided as a part of the processor 53 or may be provided separately from the processor 53. Further, the function of the control circuit 351 may be realized by dedicated hardware, by causing a general-purpose processor to execute software, or a combination thereof.
Further, in FIG. 28, an example in which control is performed based on the voltage value of the induced voltage generated in the sensing coil 317 has been described, but the same control can be performed by using the current value of the induced current.

[6. Another example of controlling the lighting interval of the beam according to the scanning position in the main scanning direction (FIGS. 31 and 32)]
Next, another example of controlling the lighting interval of the beam according to the scanning position of the emitted light L2 in the main scanning direction will be described.
The control described here is a control applied when the actuator 400 is used for the scanning unit 30. Similar control can be applied when the actuator 400'is used. The basic concept of this control is the same as the control described with reference to FIGS. 25 to 30, and the method of detecting the scanning position or angle of the mirror 401 is mainly different. Therefore, this control will be mainly described.

FIG. 31 is a perspective view corresponding to FIG. 14 showing the configuration of the actuator 400 ″, which is a modification of the actuator 400 when controlling the lighting interval of the beam.
In the actuator 400 ", a notch is provided near the center of the tip end side (opposite side of the permanent magnet 410) of the mirror 401", and the detection magnet 481 is fixed there. The detection magnet 481 is arranged so that the rotation axis 404 of the mirror 401 ″ passes through the center thereof.

Further, the actuator 400 ″ includes a magnetic sensor 482 at a position facing the detection magnet 481. The magnetic sensor 482 includes a magnetic resistance element whose resistance value changes depending on the direction of the surrounding magnetic field, and the direction of the surrounding magnetic field. It is a magnetic resistance sensor (MR sensor) that outputs a current or voltage signal according to the above. By arranging this magnetic sensor 482 near the detection magnet 481, the direction of the magnetic field generated by the detection magnet 481, that is, It is possible to output a current or voltage signal according to the orientation of the detection magnet 481.

As the magnetoresistive element (MR element), various elements such as an anisotropic magnetoresistive element (AMR element), a giant magnetoresistive element (GMR element), and a tunnel magnetoresistive element (TMR element) can be used. These MR elements can detect the direction of the magnetic field with high accuracy without depending on the strength of the magnetic field, and are suitable for detecting the rotation speed of the mirror 401 ″. This magnetic sensor 482 is an actuator using a holder or the like. It may be fixed to 400 ", but it is also conceivable to position it with the actuator 400" and fix it to the structure of the scanning unit 30, or to fix it to the structure of the object detection device 10.

FIG. 32 is a diagram showing a configuration of a control circuit that controls the lighting interval of the beam. The same reference numerals were used for the parts common to FIG. 28.
The control circuit 471 shown in FIG. 32 corresponds to a periodic control unit, and is roughly divided into operations related to drive control of the drive coil 420, detection of the rotation speed of the mirror 401 ″, and control of the lighting interval of the LD module 21.

First, regarding the drive control of the drive coil 420, the control circuit 471 sets the scan range and period values to be executed by the actuator 400 ″ to the drive signal generation circuit 472 that generates the drive signal 473 to be applied to the drive coil 420. The drive signal generation circuit 472 generates a drive signal 473 of an appropriate level having a voltage fluctuating at an appropriate cycle according to the set value and applies it to the drive coil 420 of the actuator 400 ″. As a result, as described with reference to FIGS. 17 and 18, the permanent magnet 410 can be rotated and the mirror 401 ″ can be swung by the actuator 400 ″. At this time, the detection magnet 481 also swings together with the mirror 401 ″.

Next, regarding the detection of the rotation speed of the mirror 401 ″, the magnetic sensor 482 detects the direction of the detection magnet 481 in real time and outputs a current or voltage signal according to the direction. ADC (Analog Digital Converter) The 483 converts the signal output by the magnetic sensor 482 into a digital value in real time and supplies it to the scanning speed calculation circuit 484. The scanning speed calculation circuit 484 detects the signal level of the magnetic sensor 482 stored in advance. Based on the correspondence with the angle with the magnet 481, the signal supplied from the ADC 483 is converted into the angle of the detection magnet 481, and from the time change, the rotational speed of the detection magnet 481, that is, the mirror 401 ″ The rotation angle speed (scanning speed) is obtained and supplied to the control circuit 471.
When the change in scanning speed supplied to the control circuit 471 is plotted with the time for half a cycle from one end to the other end of the swing range of the mirror 401 ″ on the horizontal axis, FIG. 25 shows, as shown in Graph 491. It is considered that the shape is almost the same as the graph of the rotational angular velocity shown.

The control circuit 471 uses the angular velocity ω (t) of the mirror 401 ″ at each time t supplied from the ADC 483 to light the LD module 21 so that a desired resolution can be obtained on the scanning line 71a in the main scanning direction. If the resolution is ψ degrees, then T = π · (ψ / 180) / ω (t). For example, ψ = 0.1 can be considered.
In order to control the lighting interval of the LD module 21, the control circuit 471 obtains the lighting interval T in real time according to the supply of the angular velocity ω (t) from the ADC 483, and obtains a pulse width modulation signal indicating the value of the T. It is supplied to the pulse generator 358.

The function of the pulse generator 358 is the same as in the case of FIG. 28. Further, the pulse interval supplied by the control circuit 471 to the pulse generator 358 is also as shown in Graph 362, as in the case of FIG. 28. This is because the actuator 400 ″ also reciprocates and rotates the mirror using a system having a restoring force to the neutral position like the actuator 300, so that the relationship between the scanning position and the scanning speed is the same as that of the actuator 300. Because they are similar.
Therefore, according to the configurations of FIGS. 31 and 32, the beam spots 72 can be arranged on the scanning line 71a in the main scanning direction at substantially equal intervals over the entire length thereof, as in the case of FIG. 28.

As the magnetic sensor 482, a sensing coil or a Hall element can also be used. Further, it is not essential to provide the detection magnet 481 near the center of the end of the mirror 401 ", and it can be provided at any position as long as the change in magnetic force can be detected by the magnetic sensor 482. In order to improve the detection accuracy, it is preferable that the magnet 410 side is not used.
Further, instead of the magnetic sensor 482, it is also conceivable to detect the angle of the mirror 401 ″ by optically detecting the position of the marker provided on the mirror 401 ″ or the mirror 401 ″. In this case, for detection. The magnet 481 is unnecessary.

[7. Other variants]
Although the description of the embodiment is completed above, in the present invention, the specific configuration of the device, the specific operation procedure, the specific shape of the component, and the like are not limited to those described in the embodiment.
Further, the features described in the above items can be independently applied to the device or system. In particular, the actuator 300, the actuator 400, the mover 320 and the like can be distributed as individual parts. Moreover, the application is not limited to the object detection device.
Further, the above-mentioned object detection device 10 can be configured to have a size that fits in the palm of a person, and is suitable for being mounted on a moving body such as an automobile or a drone and used as an obstacle detection device for automatic driving. However, its purpose of use is not limited to this. It can also be fixed to a pillar or wall and used for fixed point observation.

Further, in the embodiment of the program of the present invention, one computer or a plurality of computers are made to cooperate to control the required hardware, and the light emission of the LD module 21 in the object detection device 10 in the above-described embodiment. It is a program for realizing a function including a timing adjustment function or executing the process described in the above-described embodiment.

Such a program may be stored in a ROM provided in the computer or another non-volatile storage medium (flash memory, EEPROM, etc.) from the beginning. It can also be recorded and provided on any non-volatile recording medium such as a memory card, a CD, a DVD, or a Blu-ray disc. Furthermore, it is also possible to download it from an external device connected to the network, install it on a computer, and execute it.

Further, it goes without saying that the configurations of the embodiments and the modifications described above can be arbitrarily combined and implemented as long as they do not contradict each other, and only a part of them can be taken out and implemented.

10 ... object detection device, 20 ... light projecting unit, 21 ... LD module, 22 ... laser drive circuit, 23 ... light projecting optical system, 30 ... scanning unit, 31 ... mirror, 32 ... actuator, 40 ... light receiving unit, 41, 48 ... Mirror, 42 ... Condensing lens, 43 ... Light receiving element, 44 ... Aperture, 51 ... Front end circuit, 52 ... TDC, 53 ... Processor, 54 ... Input / output unit, 61 ... Top cover, 62 ... Rear cover, 63 ... Cover clip, 64 ... protective material, 70 ... field of view, 71 ... scanning line, 72 ... spot, 300, 380, 400, 400', 400 "... actuator, 301 ... mirror unit, 301a ... first mirror, 301b ... second Mirror, 301a1 ... 1st reflecting surface, 301b1 ... 2nd reflecting surface, 302 ... Twisting spring, 304,384,404 ... Rotating shaft, 311 ... Core yoke, 312 ... Frame yoke, 313 ... Coil assembly, 314 ... Top yoke, 315 ... Screw, 316 ... Drive coil, 317 ... Sensing coil, 320 ... Movable, 321 ... Permanent magnet, 321s ... S pole, 321n ... N pole, 381, 401, 401 "... Mirror, 382 ... Axis, 383 ... Holder, 402,402'... Mirror holder, 403,405 ... Bearing, 406,406' ... Magnet holder, 410,410' ... Permanent magnet, 410s ... S pole, 410n ... N pole, 420 ... Drive coil, 421,422 ... Drive 1st and 2nd parts of the coil, 423,424 ... 1st and 2nd connection parts of the drive coil, 430, 440, 450, 460 ... Yoke, 431-433 ... 1st to 3rd parts of the yoke 430, 441 442 ... First and second parts of yoke 440, 451-452 ... First and second parts of yoke 450, 481 ... Detection magnet, 482 ... Magnetic sensor, L1 ... Laser beam, L2 ... Emission light, L3, L4 … Return light

Claims (22)

A torsion spring fixed to the support member,
A permanent magnet fixed to the torsion spring and having an N pole on one side and an S pole on the other side across the rotation axis of the torsion spring.
A drive coil arranged on the opposite side of the permanent magnet to the torsion spring,
A drive unit that applies a drive signal whose voltage or current changes periodically to the drive coil, and
A mirror unit fixed to the torsion spring and arranged on the opposite side of the magnet, the first reflecting surface located near the center of the torsion spring and the first reflecting surface located around the first reflecting surface. A mirror unit having a second reflecting surface parallel to the reflecting surface is provided.
The plane including the second reflecting surface is closer to the rotation axis of the torsion spring than the plane including the first reflecting surface.
An actuator characterized in that the mirror unit reciprocates in response to the application of the drive signal. The actuator according to claim 1.
An actuator characterized in that the center of gravity of the mirror unit is substantially on the rotation axis of the torsion spring. The actuator according to claim 1 or 2.
An actuator characterized in that the mirror unit includes a first mirror including the first reflecting surface and a second mirror including the second reflecting surface. The actuator according to claim 3.
An actuator characterized in that the center of gravity of the second mirror is located closer to the rotation axis of the torsion spring than the center of gravity of the first mirror. The actuator according to any one of claims 1 to 4.
An actuator characterized in that the center of gravity of a mover including the torsion spring, the mirror unit, and the permanent magnet is substantially on the rotation axis of the torsion spring. The actuator according to any one of claims 1 to 5 is provided.
An optical scanning device characterized in that a light beam is reflected by a first reflecting surface of the mirror unit and then projected. The actuator according to any one of claims 1 to 5.
A laser light source that outputs a laser beam and
With the light receiving element
The laser beam is reflected by the first reflecting surface of the mirror unit and then projected to the outside, and incident light incident from the outside is guided to the light receiving element on the same optical axis as the projected light. The guiding optical system and
Object detection that detects the distance of the laser beam to an object on the optical path and the direction of the object based on the light projection timing and projection direction of the laser beam and the timing of the light detection signal output by the light receiving element. An object detection device including a unit. The object detection device according to claim 7.
A detection unit that detects the rotation speed of the mirror unit and
An object detection device including a cycle control unit that controls a blinking cycle of the laser light source according to a rotation speed detected by the detection unit. A columnar magnet with S and N poles facing each other across the central axis.
A support portion that rotatably supports the magnet around the central axis,
A drive coil arranged in the vicinity of the magnet, the first portion including a bundle of conductors parallel to the central axis and the first portion including a bundle of conductors parallel to the central axis and facing in the opposite direction to the first portion when energized. The second part through which the current flows is the drive coil arranged at a position facing each other across the magnet.
A yoke arranged on the outside of the drive coil along the central axis, wherein the distance from the central axis to the yoke on a plane perpendicular to the central axis differs depending on the direction from the central axis. ,
An actuator comprising a drive unit for applying a drive signal whose voltage or current changes periodically to the drive coil. The actuator according to claim 9.
An actuator characterized in that the magnet is cylindrical. The actuator according to claim 10.
An actuator characterized in that the magnet is prismatic. The actuator according to any one of claims 9 to 11.
When no voltage is applied to the drive coil, the magnet moves towards a neutral position in a particular orientation.
An actuator characterized in that the first portion and the second portion of the drive coil are located at positions facing each magnetic pole of the magnet at the neutral position, respectively. The actuator according to any one of claims 9 to 12.
When no voltage is applied to the drive coil, the magnet moves towards a neutral position in a particular orientation.
The distance from the central axis to the yoke is equal between the north pole side and the south pole side of the magnet in the neutral position, and the north pole and the south pole of the magnet are from the central axis in the neutral position. An actuator characterized in that the distance to the yoke faces the closest direction. The actuator according to any one of claims 9 to 13.
The drive coil is connected to one end of the second portion so that a lead wire wraps around the central axis of the magnet from one end of the first portion along the surface of the magnet, and the second portion. The actuator is formed so as to be connected to the other end portion of the first portion so as to wrap around the central axis of the magnet along the surface of the magnet from the other end portion of the magnet. The actuator according to any one of claims 9 to 14.
An actuator characterized in that the magnet reciprocates and rotates in a range centered on a position in a state where the drive signal is not applied in response to the application of the drive signal. The actuator according to any one of claims 9 to 15.
A mirror fixed to the longitudinal end of the magnet
An actuator characterized in that the mirror reciprocates and rotates in a range centered on a position in a state where the drive signal is not applied in response to the application of the drive signal. The actuator according to claim 16.
An actuator characterized in that a second magnet is provided at an end of the mirror other than the magnet side. The actuator according to claim 16 or 17 is provided.
An optical scanning device characterized in that a light beam is reflected by the mirror and then projected. The actuator according to claim 16 or 17,
A laser light source that outputs a laser beam and
With the light receiving element
An optical system that projects the laser beam to the outside after being reflected by the mirror, guides incident light incident from the outside, and guides it to the light receiving element.
Object detection that detects the distance of the laser beam to an object on the optical path and the direction of the object based on the light projection timing and projection direction of the laser beam and the timing of the light detection signal output by the light receiving element. An object detection device including a unit. The object detection device according to claim 19.
A detection unit that detects the rotation speed of the mirror,
An object detection device including a cycle control unit that controls a blinking cycle of the laser light source according to a rotation speed detected by the detection unit. The object detection device according to claim 20.
The mirror of the actuator includes a second magnet at an end other than the magnet side.
The detection unit includes a magnetic sensor provided at a position facing the second magnet, and detects the rotation speed of the mirror based on the magnetic fluctuation detected by the magnetic sensor. The object detection device according to claim 21.
The magnetic sensor is an object detection device characterized in that it is a magnetic resistance sensor that detects the direction of a magnetic field by a magnetic resistance element.

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